This invention generally relates to a screen on which a color picture is projected by means of a color television projector having red, green and blue light emitting tubes. More particularly, the present invention relates to such a screen of the type arranged to pass the light beams from the light emitting tubes applied to the screen from one side thereof to the other side, where the three light emitting tubes are arranged in-line.
As shown in FIG. 1, in some conventional projecting systems of this sort, three color light beam sources, namely, red tube 1, a green tube 2 and a blue tube 3 are arranged in line on a horizontal axis (not shown) with a given interval therebetween. Each of the tubes emits a light beam of a specified color, i.e. red, green and blue, to project a picture on a screen 4, where the three tubes are oriented to a given point A on the screen. With this arrangement, three pictures of different colors are superimposed on another at the screen so as to form or reproduce the original color picture thereon.
The reference numerals 1', 2' and 3' indicate the directivity patterns of light beams from the respective tubes 1, 2 and 3. In the case that the directivety of each color beam is very sharp, the picture on the screen partially looks bluish or reddish depending on the difference in the intensity of the light beams when a viewer moves to a point B or C because the light beam emitting tubes 1 and 3 have given angles with respect to a center axis X which is perpendicular to the screen 4.
In some of conventional screens of this sort, lenticular lens arrangement is formed on one surface of the screen. Namely, a number of elongate strips, whose transverse cross-section takes a semicircular shape, are successively formed on one surface of the screen.
The inventors of the present invention have made various researchs so as to find a way for removing the above-mentioned disadvantage or drawback inherent to the conventional screens. It has been found by the inventors, as a result, that if the cross-section of each lenticule element constituting the lenticular lens arrangement of the screen were so shaped that each dome-like shape of the cross-section is formed of a complex curve of a quadratic or higher order function, the conventional problem would be removed in theory. However, this method is not practical because it is very troublesome and also difficult to manufacture a mold for forming the screen. Namely, if it is intended to manufacture a screen having such a lenticular lens arrangement on the surface thereof, a cutter blade for forming such a complex curve has to be manufactured first in accordance with a complex program obtained as a result of various calculations. Then the cutter blade has to be precisely controlled to form a given shaped mold so as to produce a screen. It is obvious in view of nowaday machining technique that such a fine machining of the cutter blade as well as the mold is nonpractical, while such a way of manufacturing the screen results in a high manufacturing cost. The inventors has continued research, and finally found a simple shape of the cross-section of each lenticule element, so that a corresponding mold can be readily manufactured by simple machining, while the conventional problem in connection the above-mentioned bluish or reddish picture depending on the view point has been eliminated.